1. Technical Field
This invention relates to a four-axis lathe NC program creation method and, more particularly, to a method of creating NC programs for a four-axis lathe which includes a balance cutting process.
2. Description Art
In controlling the machining of a simultaneous four-axis lathe having first and second tool rests, there are provided first and second NC programs corresponding to respective ones of the tool rests and having queuing commands. While synchronization is achieved by the queuing commands, movement of the corresponding tool rests is controlled independently by the first and second NC programs to subject a workpiece to machining. With a simultaneous four-axis lathe, therefore, machining time can be shortened by e.g. machining the external form of a workpiece by the tool mounted on one tool rest and, at the same time, machining the inner diameter of the workpiece by the tool mounted on the other tool rest.
A four-axis lathe makes cutting referred to as "balance cutting" possible so that elongated, slender workpieces can be subjected to highly precise turning. When an elongated, slender workpiece WK is machined in accordance with this cutting method, as illustrated in FIG. 9, first and second tools TL1, TL2 are brought into contact with the workpiece from both sides thereof and the tools are moved synchronously in symmetric fashion to machine the workpiece simultaneously. Flexing of the workpiece can be prevented to enable highly precise machining, and it is possible to subject the workpiece to a heavy machining operation. In FIG. 9, CHK represents a chuck.
The NC programs for such a four-axis lathe are created automatically in conversational fashion by the automatic programming function of an NC unit or by a separately provided automatic programming unit.
The conventional automatic programming unit, however, does not possess a function for automatically creating an NC program for balance cutting. For this reason, a programming operation for a case where a balance cutting process is included is troublesome.
Accordingly, an object of the present invention is to provide a four-axis lathe NC program creation method through which it is possible to automatically create an NC program which includes NC data for balance cutting.